1. Field of the Invention
The present invention relates to a droplet jetting applicator that jets and thus applies multiple droplets to an object to be coated, and also relates to a method for manufacturing a coated body.
2. Description of the Related Art
Droplet jetting applicators have been used not only for printing of image information, but also for a process of manufacturing various kinds of flat display devices, such as liquid crystal display devices, organic electro luminescence (EL) display devices, electron emission display devices, plasma display devices, and electrophoretic display devices.
Such a droplet jetting applicator includes a droplet jetting head (for example, an inkjet head) that jets droplets of a liquid, such as an ink, from multiple nozzles thereof to an object, such as a substrate, to which the liquid is to be applied (hereinafter, such object will be referred to as an application target). Multiple droplets are jetted to land on the application target by the droplet jetting head, so that a predetermined application pattern is formed. In this manner, various kinds of coated bodies are manufactured.
The ink is supplied from an ink tank to the droplet jetting head through a pipe (ink channel). The pipe is provided with a valve, a pump and the like. Note that, the liquid pressure of the ink in the droplet jetting head is maintained at a negative pressure in order to prevent troubles, such as the leakage of the ink from the nozzles (see, for example JP-A No. 2006-192638(KOKAI)).
Such a droplet jetting applicator uses ink containing an almost insoluble material. When such ink is deteriorated with time, the material thereof settles down. This settling causes jetting failure in the droplet jetting applicator. To solve this problem, there has been proposed a droplet jetting applicator in which ink circulates between a droplet jetting head and an ink tank (see, for example, JP-A No. 2004-230652(KOKAI)).
However, in the above-described droplet jetting applicator, pressure fluctuation caused by the drives of the valve and pump is transmitted to the droplet jetting head through the ink in the pipe, and causes leakage of the ink, absorption of air, and the like. As a result, exudation of the ink to a nozzle surface and absorption of air bubbles into the droplet jetting head are caused, thereby resulting in jetting failure such as a non-jetting problem.